How to create Cross-Section view in 3D Unstructured Meshes

Hi Every body.
Rencently I was building a model with 3D Unstructured Meshes, I want know How to create Cross-Section view in 3D Unstructured Meshes like this video(https://www.youtube.com/watch?v=GsIDtot6HNs&list=PLoEU6vvsKI94tFPmFmvQEPpQAD0lewAPT),The FEFLOW Help system only mentioned Cross-sections can be created in the Slice view by using the Draw a Surface (2D) Line tool,but don't say How do it in 3D Unstructured Meshes.

You could build up a dummy layer-based model on the same model area, and create the 2D cross-section lines. Then you could export the lines and import to 3D unstructured mesh.

Alternatively, you can import the polylines from any external file (e.g., a Shapefile) and then do a right-click on the file name. Here FEFLOW will offer you an option to convert to Location Sets.